Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
Coatings are applied to a wide variety of substrates for widely divergent purposes. Examples of the many different types of coatings in use include adhesive coatings, primer coatings, decorative coatings, protective hard coatings, anti-reflective coatings, reflective coatings, interference coatings, release coatings, dielectric coatings, photoresist coatings, conductive coatings, barrier coatings, and the like. Such coatings can be applied to substrates that are made from many different materials and have many different shapes. For example, in terms of materials, substrates may be metal, polymeric, ceramic, paper, mineral, glass, composite, and the like. In terms of shape, substrates may be flat, curved, undulating, smooth, rough, porous, particulate, fibrous, regular or irregular surfaced, and the like.
In conventional industrial coating processes, an admixture (for example, an emulsion, solution, slurry, two-phase fluid mixture, and the like) comprising the coating constituents and a suitable solvent is applied to the substrate using a suitable coating technique such as spraying, roll coating, brush coating, spin coating, or the like. The coated composition is then typically dried and cured in order to solidify the coating. During drying, the solvent is removed from the coating and then discarded or recovered.
Several solvent-free methods which avoid the expense or problems associated with removal, disposal, or recovery of solvents have been described for the deposition of thin polymer films onto substrates, such as polymers, metallized polymers, or metal foils and the like. For example, in U.S. Pat. No. 5,260,095 to Affinito, is described a method of depositing a thin layer of liquid monomer onto a moving substrate in a vacuum chamber and curing the thin layer. In U.S. Pat. No. 4,842,893 to Yializis et al. is described a coating method in which flash evaporation of monomer fluids from a heated surface forms vapor which is condensed on a substrate as a thin film and polymerized. In U.S. Pat. No. 6,045,864 to Lyons et al. is described a vapor coating method in which a carrier gas vaporizes a fluid composition and carries the vapor to a substrate upon which the vapor condenses and may be polymerized to form a coating. J. Affinito et al. (Affinito 1) in Proceedings of the Fourteenth International Conference on Vacuum Web Coating, pp. 77–94, ed. R. Bakish, Bakish Press (2000), and J. Affinito et al. (Affinito 2) in Proceedings of the 44th Annual Technical Conference of the Society of Vacuum Coaters, pp. 492–497 (2001), describe a thermal evaporation process and theoretical modeling for the deposition of lithium metal on polymer films.
There is a need for less costly and simpler solvent-free methods for providing thin film coatings for a variety of applications.